Back when Christopher Nolan‘s Interstellar was in theaters, Peter wrote a very detailed breakdown of the differences between the original script by Jonathan Nolan, written for Steven Spielberg, and the version that Christopher Nolan shot with his own revisions. Now Jonathan Nolan has talked about some of differences between his script and the finished film while promoting the blu-ray release of the film. Specifically, he addressed the ending, which as originally written in one draft — potentially a different one from the 2008 Spielberg draft — was much more simple, and potentially far less happy.

Spoilers for Interstellar follow.

During a speaking gig at Caltech’s Jet Propulsion Lab in Pasadena with physicist and adviser Kip Thorne, Nolan was asked exactly what happened at the end of the film. He joked “You’ve got the wrong brother.”

But he did talk a bit about his original ending, which was “much more straightforward” and in which “the Einstien-Rosen bridge [colloquially, a wormhole] collapsed when Cooper tries to send the data back.”

In other words, a lot of the stuff we see at the end of the film as it exists now possibly happen. Nerdist, reporting on the event, speculates that instead of Cooper (Matthew McConaughey) going into the black hole Gargantua and finding himself inside the tesseract, he would never have been able to manipulate time or contact his young daughter, or return to Earth. But the draft Peter wrote about had some other differences in the ending, with Cooper in fact getting back to Earth, but with many details different from the finished film.

And Kip Thorne, at the same event yesterday, explained another difference:

The gravitational anomalies that pointed Cooper and his daughter toward the remnants of NASA were initially supposed to be gravity waves emanating from the destruction of a neutron star via black hole. Since the waves could only be produced by something so catastrophic, and we know nothing like that exists in our solar system, the waves detected must be coming out of some wormhole close to us, Kip Thorne explained to the audience.

That’s also different from the draft Peter wrote about, in which a downed space probe provides the guide to NASA. So, as you would probably expect, there are likely a couple versions of the script floating around, with the details provided at this talk pointing to a draft that was written in the time between the early one we’ve previously discussed, and the final shooting draft.